JPT-06855; No of Pages 10 Pharmacology & Therapeutics xxx (2016) xxx–xxx Contents lists available at ScienceDirect Pharmacology & Therapeutics journal homepage: www.elsevier.com/locate/pharmthera Insight into SUCNR1 (GPR91) structure and function Julie Gilissen a,b, François Jouret c,d, Bernard Pirotte b, Julien Hanson a,b,⁎ a Laboratory of Molecular Pharmacology, GIGA-Molecular Biology of Diseases, University of Liège, Liège, Belgium b Laboratory of Medicinal Chemistry, Centre for Interdisciplinary Research on Medicines (CIRM), University of Liège, Belgium c Laboratory of Experimental Surgery, GIGA-Cardiovascular Sciences, University of Liège, Liège, Belgium d Division of Nephrology, University of Liège Hospital (ULg CHU), Liège, Belgium article info abstract Keywords: SUCNR1 (or GPR91) belongs to the family of G protein-coupled receptors (GPCR), which represents the largest SUCNR1 group of membrane proteins in human genome. The majority of marketed drugs targets GPCRs, directly or GPR91 indirectly. SUCNR1 has been classified as an orphan receptor until a landmark study paired it with succinate, a Succinate citric acid cycle intermediate. – Ischemia reperfusion injury According to the current paradigm, succinate triggers SUCNR1 signaling pathways to indicate local stress that Hypertension may affect cellular metabolism. SUCNR1 implication has been well documented in renin-induced hypertension, Diabetes ischemia/reperfusion injury, inflammation and immune response, platelet aggregation and retinal angiogenesis. In addition, the SUCNR1-induced increase of blood pressure may contribute to diabetic nephropathy or cardiac hypertrophy. The understanding of SUCNR1 activation, signaling pathways and functions remains largely elusive, which calls for deeper investigations. SUCNR1 shows a high potential as an innovative drug target and is probably an impor- tant regulator of basic physiology. In order to achieve the full characterization of this receptor, more specificphar- macological tools such as small-molecules modulators will represent an important asset. In this review, we describe the structural features of SUCNR1, its current ligands and putative binding pocket. We give an exhaus- tive overview of the known and hypothetical signaling partners of the receptor in different in vitro and in vivo systems. The link between SUCNR1 intracellular pathways and its pathophysiological roles are also extensively discussed. © 2016 Elsevier Inc. All rights reserved. Contents 1. SuccinateReceptor1structureandligands................................. 0 2. SuccinateReceptor1signalingpathways.................................. 0 3. Implicationin(patho)physiology...................................... 0 4. Conclusion................................................ 0 Conflictofinterest............................................... 0 Acknowledgments............................................... 0 References.................................................. 0 Abbreviations: (GPCRs), G protein-coupled receptors family; (SUCNR1), succinate receptor 1; (AA), amino acids; (7TM), seven transmembrane domains; (ECLs), extracellular loops; (ICLs), intracellular loops; (cAMP), cyclic adenosine monophosphate; (AC), adenylate cyclase; (GRKs), G protein-coupled receptor kinases; (CHO) cells, Chinese hamster ovary; (HEK293) cells, human embryonic kidney; (MDCK) cells, madin darby canin kidney; (iDC), immature dendritic cells; (PTX), pertussis toxin; (ERK1/2), extracellular signal-regulated kinases 1 and 2; (RGC), retina ganglion cells; (RAS), renin–angiotensin system; (JGA), juxtaglomerular apparatus; (MD), macula densa; (JG) cells, juxtaglomerular; (COX-2), cyclooxygenase 2; E2 (PGE2), prostaglandin; (PGI2), prostaglandin I2; (AA), arachidonic acid; (GENCs), juxtaglomerular endothelium cells; (NO), nitric oxide; (CH), cardiac hypertrophy; (CaMKIIδ), calcium/ calmodulin-dependent protein kinase IIδ; (HDAC5), histone deacetylase 5; (PKA), protein kinase A; (PLN), phospholamban; (RyR2), ryanodine receptor 2; (PDE), phosphodiesterase; (RVH), right ventricular hypertrophy; (LVH), left ventricle hypertrophy; (PI3K), phosphatidylinositol-4,5-bisphosphate 3-kinase; (Akt), protein kinase B; (WAT), white adipose tissue; (MS), metabolic syndrome; (ASA), acetylsalicylic acid; (ADP), adenosine diphosphate; (TXA2), thromboxane A2; (DR), diabetic retinopathy; (VEGF), vascular endothelial growth factor; (JNK), c-Jun N-terminal kinases; (ROP), retinopathy of prematurity; (CHI), cerebral hypoxic–ischemic; (EP4), prostaglandin E receptor 4; (AMD), age-related macular degeneration; (RPE), retinal pigment epithelium; (FSK), forskolin; (HSC), hepatic stellate cells; (α-SMA), α-smooth muscle actin; (HPC), hematopoietic progenitor cells; (IP), inositol phosphate; (iDC), imma- ture dendritic cells; (TNF-α), tumor necrosis factor α; (IL-1β), pro-inflammatory cytokine interleukin-1 beta; (IFN-γ), interferon γ; (IRI), ischemia–reperfusion injury. ⁎ Corresponding author at: Laboratory of Molecular Pharmacology, GIGA-Molecular Biology of Diseases, University of Liège, Quartier Hôpital, Avenue de l'hôpital, 11, 4000 Liège, Belgium. E-mail address: [email protected] (J. Hanson). http://dx.doi.org/10.1016/j.pharmthera.2016.01.008 0163-7258/© 2016 Elsevier Inc. All rights reserved. Please cite this article as: Gilissen, J., et al., Insight into SUCNR1 (GPR91) structure and function, Pharmacology & Therapeutics (2016), http://dx.doi.org/10.1016/j.pharmthera.2016.01.008 2 J. Gilissen et al. / Pharmacology & Therapeutics xxx (2016) xxx–xxx 1. Succinate Receptor 1 structure and ligands structure. Recently, many crystallographic data for class A GPCRs bound to different ligands, in different crystal forms or using different SUCNR1 was first spotted in a megacaryocytic cell line in 1995 and approaches to receptor stabilization and crystallization have been called “P2U2”, a name coined for its homology with the purinergic recep- disclosed (a complete listing is outside the scope of this article but tor P2Y2, known as P2U at that time (Gonzalez et al., 2004). SUCNR1 readers may find complete information in recent reviews (Katritch gene was later re-discovered as GPR91 in 2001 on human chromosome et al., 2013; Zhang et al., 2015)). Although SUCNR1 has not been crystal- 3q24–3q25 using an expressed sequence tag data mining strategy lized yet, the information on its structure can be hypothesized by com- (Wittenberger et al., 2001). Of important note is the possibility of two parison with closely related proteins. Two representative purinergic open-reading frames (ORF) for SUCNR1, one giving a protein of 330 receptors (P2Y1 and P2Y12) have been crystallized recently (Zhang amino acids (AA) and the other one 334 AA. Wittenberger et al. noted et al., 2015; Zhang J. et al., 2014; Zhang K. et al., 2014) and some careful that the 330-AA protein was more likely to be expressed given the inferences can be made on SUCNR1 structure. Kozak sequence surrounding the second ATG (Wittenberger et al., 2001). In the present article we will use the AA numbering according 1.1. Extracellular domains to a 330-AA protein, although the current databases sometimes report SUCNR1 as being 334-AA long. There is a high degree of homology SUCNR1 shares with GPCRs the general extracellular structure between man and mouse (68%) with the exception of the C-terminal where transmembrane domains are connected by three hydrophilic tail, which is 12 AA shorter in rodents (Ariza et al., 2012; Wittenberger extracellular loops (ECLs). A disulfide bond highly conserved among et al., 2001). In humans, other genes have been found on the same GPCRs links the top of the TM3 (at the end of ECL1) to the middle of locus and consist in a cluster of P2Y1, P2Y12, P2Y13,H963(GPR171) and ECL2 and is present in many GPCRs. The presence of two conserved GPR87 (Abbracchio et al., 2006). In their seminal paper, Wittenberger cysteines in ECL2 (C168) and top of TM3 (C913.25) suggests that et al. speculated that all these receptors originated from a common an- SUCNR1 possesses this canonical disulfide bridge (Fig. 1). cestor, presumably a nucleotide receptor (Wittenberger et al., 2001). A second conserved disulfide bridge is often observed between Several comprehensive reviews have been published on the receptor the N-terminus of the receptors and the top of TM7 (or at the end or succinate role in metabolic/oxidative stress conditions (Ariza et al., of ECL3). It stabilizes the extracellular structures and forms a pseudo- 2012; Peti-Peterdi et al., 2013). The present work, in addition to loop that has recently been defined as “ECL4” (Szpakowska et al., discussing the most recent developments, considers extensively the 2014). This feature is present in both P2Y12 and P2Y1 crystal structures mechanisms linking SUCNR1-activated signaling pathways and all (Zhang et al., 2015; Zhang J. et al., 2014). It is tempting to speculate that (patho)physiological states where the receptor might play a role. SUCNR1 has a similar architecture since it has two cysteines positioned SUCNR1 belongs to G protein-coupled receptors (GPCRs) family. In at topologically similar positions (C7 and C2647.26). Resolution of the human genome, it is the largest group of proteins involved in signal SUCNR1 crystal structure is expected to confirm the presence of the transduction across biological membranes (Fredriksson et al., 2003). disulfide bonds and mutations of these residues should show if the GPCRs are currently the direct or indirect target for ~60% of marketed bridges are critical for interactions